It is a common practice during agricultural spraying operations to reload the sprayer tank from a tank carried by a nurse vehicle. Oftentimes the nurse tank liquid level is lower that the sprayer pump inlet, especially when the sprayer pump is used with a high clearance sprayer vehicle where the pump is mounted high on the vehicle chassis. A centrifugal pump is a cost effective method of transferring fluid quickly, but such pumps are not able to prime themselves when the liquid source is lower than the pump inlet. Therefore, it is common in the industry to mount centrifugal transfer pumps on the nurse vehicle in a location lower than the liquid level of the nurse vehicle tank.
However, locating a centrifugal transfer pump on the nurse vehicle has some disadvantages in cost, automation and versatility. Specifically, more than one nurse vehicle is often required to service one sprayer. This requires having a transfer pump on each of several nurse vehicles.
While many sprayer manufacturers use centrifugal pumps because they are cost effective and easy to service, and have in the past provided systems which permitted these pumps to serve also as transfer pumps, the aforementioned problem requiring the pumps to be primed when used as transfer pumps has not been adequately resolved, with the result that unprimed pumps may be run dry for a period of time that causes pump failure. Although positive displacement pumps can be used instead of centrifugal pumps since they can be primed from a liquid level lower than the pump inlet, these pumps have the drawbacks of being high in cost and of requiring more time to transfer the fluid.
The problem to be solved then is that of providing a sprayer vehicle with a centrifugal spray pump that can also be used as a transfer pump but which can be easily and reliably primed in the event that the nurse tank fluid level is below the inlet of the pump.